258. Add Digits

class Solution(object):
    def addDigits(self, num):
        """
        :type num: int
        :rtype: int
        """
        sum=num%10
        a=num/10
        if a >=1:
            while a > 9:
                sum += a%10
                a=a/10
            sum += a
        if sum <10:
            return sum
        else:
            return self.addDigits(sum)